Process for concentrating ores



Patented .Iune 1940 j UNITED STATES PATENT OFFICE PROCESS FOR CONCENTRATING OBES Henry A. Doerner and Dwight L. Harris, Pullman,

Wash., assignors to State College 0! Washington Research Foundation, Pullman, Wash.

No Drawing. Application January 9, 1939,

Serial No. 249,895

8 Claims.

air bubbles, and are carried upward into a floating froth. In a flotation process the froth is skimmed off, thereby efiecting a separation be-.

tween the various minerals based upon the selective action of the collector. Other reagents may be used to produce a better froth or to modify the selective action of the collector. These are called frothers, activators, depressors or conditioners.

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Until recently, most, if not all collectors gave negatively charge collecting ions. Such anionic collectors are strongly adsorbed by the metallic minerals, particularly the sulphides of heavy metals. In general they have relatively little effect on non-metallic minerals. ration of metal sulphides from non-metallic minerals is easily accomplished. This selective action varies, and can be used to separate two or more easily floated minerals from'each other. Such separations are more diflicult and usually require the assistance of activators or depressors to increase or reverse the selective action of into two or more products by flotation with one type of collector, and if ,one or more of those products are subsequently subjected to a second flotation with the opposite type of collector, the selective actions in the two steps are usually cumulative. The separations thus made are more complete than can be accomplished by repeated flotation steps with only one type of collector. This is the essence of our invention.

We believe this discovery constitutes a new principle in the art of flotation. It should not be confused with the common practice whereby the'selectivity of a collector is modified or even.

reversed bv the use of addition'a'gentsf The changes in selectivity caused by addition agents Hence a sepa- Although these cationic 001- are usually cumulative when used first with one type and then with the other type of collector.

The principle can be illustrated by our process forthe concentration of magnesite ores. Magne' site, as it occurs in nature, is commonly associated and more or less intimately mixed with dolomite, calcite, talc, serpentine and quartz.

- At present, magnesite of commercial grade is obtained by selective mining, hand sorting and washing. These methods are expensive, and can not be usedto obtain a high grade product from any but the best ores.

centrate magnesite ores by flotation, but the results have not been good enough to encourage commercial application. Two general methods have been tried; the flotation'of iin'purities from the magnesite, and the flotation of magnesite from the impurities. The former gives best results with some ores, and with otherores the latter method is more effective. But in general, neither method is adequate,,and we have not found any claim that a separation has been.

made by flotation between the very similar minerals, magnesite and dolomite.

The cationic collectors are best for floating most of the siliceous material from magnesite ore. But in this case most of the dolomite and some silicates remain with the magnesite. Other investigators have shownthat magnesite can be floated with anionic collectors such as oleic acid. But in this case dolomite and some of the silicates also float and contaminate the product. The diiflculty lies in the fact that in both cases some impurities float more readily and others less readily than the, magnesite. Nor is the selectivity sufllcient to permit a clean separation by repeated flotation-steps with the same type of collector.

We have found that if a siliceous product is first removed by flotation. with cationic collectors and then it magnesite is floated from the residual pulp by anionic collectors, a good recovery 01" the magnesite is obtained and the product is of much better grade than can be produced by previous methods. We have also found that the increased selectivity caused by certain conditioning reagents, such as tannin, is in this case also cumulative.

For example, with cationic collectors, dolomite floats better than magnesite and the ratio of magnesite to dolomite is lower in the floated product than in the original material. When Several investigators have attempted to con-,

magnesite is subsequently floated with anionic,

' collectors, it floats more readily than dolomite,

tive. The selectivity in each step, however, is ..so weak. that even the cumulative separation is poor. But tannic acid, for example, will cause an increased selectivity in both steps and the and thus the two separating eflects are cumulaanalysis of the crude ore.

covery of the' total MgO. (See last column. of

the table.) When magnesite is heated to a high temperature it liberates C02 and is converted to MgO. The resulting 'calcine only weighs about half as much as the ore. The analyses in thetable represent the composition of the calcined products.

In test #119 magnesite was floated with oleic, acid. The ratio of MgO to vCaO is slightly higher in this concentrate than in the crude ore.

In test #127 the pulp was conditioned'with tannin and water glass, and then magnesite was floated with oleic acid. The ratio of MgO to C80 with the cationic collector, "D. P. 243.

has been improved and the recovery is also higher;

In test #115 a siliceous product was floated In this case the concentrate is thematerial that failed to float. Although the ratio of MgO to 0110 was 'to produce and remove a froth containing maglector in one or both only slightly improved, the grade and recovery are both better than was obtained in the previous tests.

.Data from flotation tests I P t Analysis ofcalcineborcent P ,t

eroen crew of to 53535: 0! total Si'O; 38: 0B0 MgO M Ore 45.8 1&7 2.3 17.2 66.8

Concentrates No. 4 119 64.8 4&5 as 2.1.18.4 727 05.9 127 67.2 47.0 9.2 21 129 75.8 70.0 116 70.1 49.3 3.3 21 15.0 -79.0- 75.0 -147 55.4 50.3 2.4 2.1 11.4. 84.1 70.0 148 44.0 50.5 2.5 2.0 7.0 87.8 57.9 149 33.0, 50.7 2.0. 1.0 5.8 80.7 45.8 150 43.5 50.3 1.8 2.1 2.7 9a.4 57.4

In was conditioned ,with tannin and a siliceousproduct was floated with D. .P.243. Then the enriched residue was conditioned with water glass and a magnesite concentrate floated with oleic ac-id- The ratio of MgO to 09.0 is"3.9 in the ore and 7 .4, 11.5, 15.5 and 34.6-res'pectively in concentrates #147, #148, #149 and #150.

It is obvious that the order ofthe steps can be changed without departing from the spirit of the invention. For example, a concentrate floated by means of anionic collectors may be retreated by floating off impurities'with cationic collectors. Nor do we limit our invention to the treatment of anyparticular kind of ore.

weclaimz 1. The method of concentrating magnesite ore by flotation which comprises treating a water suspension of the' comminuted ore in two steps; first,

agitating and aerating the pulp with a cationic collector'to produce and remove a froth containing chiefly siliceous impurities; second, agitating and aerating the remaining pulp with oleic' acid nesite.

2. The method of concentrating magnesite ore by flotation 'which comprises treating a water tests #147, #148, #149 and #150 the pul collector suspension of the comminuted ore in two steps:

first, agitating and aerating the pulp with a cationic collector and a l'rothing agent to produce and remove a froth containing chiefly siliceous impurities; second, agitating and aerating the remaining -pulp with oleic acid to produce and remove a froth containi'ng magnesite.

3. The method of concentrating magnesite ore by flotation which comprises treating a water suspension of the comminuted one in two steps: first, agitating and aerating the pulp with a cationic collector to produce and remove a froth contain ing chiefly siliceous impurities; second, agitating ing pulp with oleic acid to produce and remove a ,froth containing magnesite, plus the addition of sodium dis'ilicate to increase the selectivity of the collector in one orboth of the flotation steps.

5. The method of concentrating magnesite ore by flotation which comprises treating a water suspension of the comminuted ore in two steps:

first, agitating 'and aerating the pulp 'with a cationic collector to produce and remove a froth containin chiefly siliceous impurities; second,.

agitating and aerating the remaining pulp wit oleic acid to produce and remove-a froth containing magn'esite, plus the addition of tannin to increase the selectivity of the collector in one or both of the flotation steps.

. 5. The method of concentrating magnesiteicre .by flotation'which comprises treating a water suspension of the comminuted ore in two steps:

' .flrst, agitating and aerating the pulp' with a cationic collector and a frothing agent to produce and remove a froth containing chiefly siliceous impurities; second, agitating and aerating the re.- maining pulp with oleic, acid to produce and remove a froth containing magnesite, plus the addition of tanninto increase the selectivity of the collector in one or both of the flotation steps. 7. The method of concentrating magnesite ore by. flotation which comprises treating a water suspension of the comminuted ore in two steps first, agitating ,and aerating the pulp with acationic to produce and remove a froth containing chiefly siliceous impurities; second, agitating and aerating the remaining pulp with oleic acid to produce and remove a froth containing magnesite, plus the addition of a starch to increase the selectivity of the collector in one or both of the flotation steps. 8. The method of. concentrating magnesite ore ,by flotation whlchcomprises treating a water suspension of the comminuted ore in two steps: first,

agitating and aerating the pulp with a cationic collector and a frothing' agent to produce and remove a froth containing chiefly siliceous impurities; second, agitatin and aerating the remainin'g pulp with oleic .ac d toproduc'eand re- .move a froth containing magnesite, plus the use of a starch .to increase the selectivity of the colof the flotation steps.- HENRY A.. DOERNER.

DWIGHT L. HARRIS. 75v 

